File and Folder names that begin or end with the ASCII Space (0x20) will be saved without these characters. File and Folder names that end with the ASCII Period (0x2E) character will also be saved without this character. All other trailing or leading whitespace characters are retained.

For example:

•If a file is saved as ' Foo.txt', where the leading character(s) is an ASCII Space (0x20), it will be saved to the file system as 'Foo.txt'.
•If a file is saved as 'Foo.txt ', where the trailing character(s) is an ASCII Space (0x20), it will be saved to the file system as 'Foo.txt'.
•If a file is saved as '.Foo.txt', where the leading character(s) is an ASCII Period (0x2E), it will be saved to the file system as '.Foo.txt'.
•If a file is saved as 'Foo.txt.', where the trailing character(s) is an ASCII Period (0x2E), it will be saved to the file system as 'Foo.txt'.
•If a file is saved as ' Foo.txt', where the leading character(s) is an alternate whitespace character, such as the Ideographic Space (0x3000), it will be saved to the file system as ' Foo.txt '. The leading whitespace characters are not removed.
•If a file is saved as 'Foo.txt ', where the trailing character(s) is an alternate whitespace character, such as the Ideographic Space (0x3000), it will be saved to the file system as 'Foo.txt '. The trailing whitespace characters are not removed.

File and Folder names that begin or end with a whitespace character are enumerated differently by the Win32 and WinRT APIs due to ecosystem requirements.

Read more at: Support for Whitespace characters in File and Folder names for Windows 8, Windows RT and Windows Server 2012